Exclusive Event Based Gateway Example

An example of an Exclusive Decision/Merge (XOR) Event Based Gateway that provides an example for workflow process pattern 16, Deferred Choice.

Workflow process pattern 16, Deferred Choice, states:

A point in a process where one of several branches is chosen based on interaction with the operating environment. Prior to the decision, all branches represent possible future courses of execution. The decision is made by initiating the first task in one of the branches i.e. there is no explicit choice but rather a race between different branches. After the decision is made, execution alternatives in branches other than the one selected are withdrawn.

The state remains on the Exclusive Event Based Gateway until a signal or message is caught, or the timer expires.

When the event occurs, the state is pulled from the Gateway to the relevant task, and this removes other paths from possible operation.

Note: It is possible to have multiple paths, with various timers, messages and signals, but the Gateway only actions the first event to occur.